Collapsible stroller frame



FIG. 1 is a side perspective view of an collapsible stroller frame, showing our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a left elevation view thereof;

FIG. 5 is a right elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines shown in the drawings illustrate environment and form no part of the claimed design. 

We claim the ornamental design for an collapsible stroller frame, as shown and described herein. 